FIG. 1 illustrates a conventional biosensor based on an electronic circuit. The conventional biosensor based on an electronic circuit can measure a result obtained by converting an amount of electric or magnetic change of bio-material to be detected to current or voltage so as to detect density and a characteristic of the bio-material. For example, when density of bio-material to be measured is changed, the resistance value of the bio-material is also changed.
Accordingly, current and voltage through the bio-material are changed so that, by using this changed value, change of density of the bio-material can be measured.
It is possible to determine if any disease exists by measuring change of an amount of blood sugar or change of density bio-material including material causing various kinds of diseases.
FIG. 2 is a view illustrating a conventional optical biosensor using a SPR phenomenon, in which the optical biosensor has undergone an etching process, and FIG. 3 is a view illustrating a conventional optical biosensor using a SPR phenomenon, in which the optical biosensor has undergone a polishing process.
A surface Plasmon Resonance (SPR) phenomenon is used in a method for measuring density of bio-material to be detected by using an optical phenomenon. So as to measure density of a specific bio-material by using an optical technique, first, a bio-material detecting part reacting to a specific bio-material has to be attached to the exterior of an optical waveguide. At this time, a typical bio-material detecting part may not be attached to an optical waveguide based on silica. Meanwhile, the bio-material detecting part has its own property allowing attachment to metal such as Au, and an optical waveguide based on silica can be easily coated with metal. Therefore, a metallic layer, which can be attached to a bio-material detecting layer as well as an optical waveguide based on silica, is inserted between the optical waveguide and the bio-material detecting layer so that the bio-material detecting layer can be combined with the optical waveguide. Therefore, a biosensor is implemented. In a case where bio-material is added to the above structured biosensor, reaction occurs in the bio-material detecting layer. At this time, an amount of physical reaction is changed according to density of bio-material. This finally causes change of refractive index. Due to such a change of refractive index in the bio-material detecting layer attached to the exterior of the metallic layer, a phenomenon that only a signal of a specific wavelength, among optical signals propagating through the optical waveguide, couples to the outside of the biosensor and disappears through the surface plasmon resonance (SPR).
A method for etching or polishing a cladding area of an optical waveguide is performed to a conventional optical biosensor so as to generate an SPR phenomenon. In case of a conventional optical biosensor, to generate the SPR phenomenon, a distance between a core area through which an optical signal propagates and an outer sensing area at which a bio-material reacts needs to be short within several micrometers. In order to achieve this, a process for etching or polishing a cladding area is a necessary process in manufacturing a sensing part of the conventional optical biosensor.
Therefore, there will be a problem in that manufacturing costs increase due to such a process for etching or polishing in manufacturing an optical biosensor.
Also, the complicate manufacturing process makes it difficult to realize the mass production of the biosensor.